Controllable fabrication of atomic dispersed low-coordination nickel-nitrogen sites for highly efficient electrocatalytic CO2 reduction.

[Display omitted] • The coordination structure of Ni single atoms can be easily controlled by the regulation of pyrolysis temperature. • The electrocatalytic CO 2 RR performance was promoted by low-coordination nickel-nitrogen sites. • Ni SA @N 3 -C displayed a maximum FE CO of 96.0% with a j CO of −18.87 mA cm−2 at −0.83 V vs. RHE. Single-atom catalysis has been considered as a powerful approach for CO 2 reduction reaction (CO 2 RR) to achieve efficient resource conversion and carbon neutrality. The electrocatalytic activity of single-atom catalysts (SACs) is closely related to the local coordination environment. Herein, Ni SACs with well-defined low-coordination nickel-nitrogen sites (denoted as Ni SA @N 3 -C) have been successfully developed via a facile sacrificial template method. XAS results reveal that the coordination environment of the atomically dispersed Ni active sites can be controlled by the pyrolysis temperature. Significantly, Ni SA @N 3 -C displays remarkably excellent activity toward electrocatalytic CO 2 RR with CO Faradaic efficiency (FE CO) of 96.0% at −0.83 V vs. RHE and remains high FE CO exceeding 90% over a broad potential range from −0.63 to −0.93 V vs. RHE, outperforming those of Ni SA @N 4 -C and Ni NP @NC. More importantly, Ni SA @N 3 -C exhibits an excellent CO selectivity of 99.2% with a considerable current density of −160 mA cm−2 in the flow cell reactor. Density functional theory (DFT) calculations further suggest that the Ni single atoms coordinated by three N atoms possesses a suitable free energy barrier for *COOH formation and *CO desorption, thereby exhibiting the most excellent CO 2 RR performance. This study sheds a new light on the design of SACs with controllable coordination structures for CO 2 RR. [ABSTRACT FROM AUTHOR]